Journey's End Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Journey's End Observatory clear sky chart from 2005-11-06 to 2026-02-01.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	12% 7% 2 6% 4 4 4 3 5% 7% 45%	127053
	Night	12% 7% 2 6% 4 4 4 3 5% 6% 48%	125205
Transparency	Day	38% 4 11% 26% 17% 4	130665
	Night	37% 4 10% 26% 19% 4	129669
Seeing	Day	15% 9% 26% 27% 17% 5%	17191
	Night	16% 9% 30% 31% 13% 1	27124

By Month

Percentage Cloud Cover SE (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	17% 11% 3 5% 5% 4 3 3 3 5% 41%	4167
	11th to 20th	Day	8% 10% 4 8% 4 5% 4 3 4 5% 44%	4170
	21st to end	Day	17% 10% 3 7% 3 3 3 3 4 5% 42%	4587
February	1st to 10th	Day	17% 12% 3 7% 5% 3 5% 3 4 5% 36%	1800
	11th to 20th	Day	14% 11% 2 7% 5% 4 4 3 4 5% 41%	1759
	21st to end	Day	15% 10% 2 6% 4 4 4 3 6% 7% 39%	1740
March	1st to 10th	Day	13% 9% 2 6% 3 3 3 3 4 5% 48%	4936
	11th to 20th	Day	11% 7% 2 4 3 3 3 3 4 6% 55%	4980
	21st to end	Day	14% 10% 3 7% 5% 5% 5% 4 6% 7% 35%	5462
April	1st to 10th	Day	13% 9% 2 6% 3 3 5% 4 5% 6% 44%	2357
	11th to 20th	Day	16% 9% 2 6% 4 3 4 3 5% 7% 41%	2374
	21st to end	Day	19% 8% 3 7% 5% 4 4 3 5% 7% 36%	2400
May	1st to 10th	Day	19% 8% 2 6% 5% 4 4 4 6% 7% 36%	5834
	11th to 20th	Day	12% 6% 3 6% 5% 4 5% 4 6% 8% 42%	5862
	21st to end	Day	19% 6% 2 6% 4 4 4 3 5% 7% 38%	6612
June	1st to 10th	Day	8% 5% 3 5% 4 4 5% 4 7% 10% 46%	2800
	11th to 20th	Day	8% 4 2 6% 5% 5% 4 4 6% 8% 47%	2800
	21st to end	Day	6% 3 1 4 3 5% 5% 4 6% 9% 55%	2788
July	1st to 10th	Day	9% 5% 3 6% 4 4 6% 5% 7% 8% 44%	5900
	11th to 20th	Day	7% 5% 2 7% 4 5% 5% 5% 7% 10% 44%	5900
	21st to end	Day	5% 4 2 6% 4 4 5% 4 7% 11% 48%	6422
August	1st to 10th	Day	5% 3 1 5% 4 4 4 4 6% 8% 56%	4234
	11th to 20th	Day	8% 5% 2 6% 5% 5% 5% 4 7% 9% 44%	4087
	21st to end	Day	6% 4 2 4 4 4 4 4 5% 8% 56%	4312
September	1st to 10th	Day	11% 6% 2 5% 4 3 4 3 5% 6% 51%	2400
	11th to 20th	Day	10% 6% 2 6% 4 5% 4 3 5% 7% 47%	2310
	21st to end	Day	8% 5% 1 5% 5% 5% 4 4 6% 7% 51%	2131
October	1st to 10th	Day	10% 5% 1 4 3 3 4 3 5% 6% 56%	2000
	11th to 20th	Day	13% 6% 2 5% 3 3 3 2 3 5% 55%	2000
	21st to end	Day	19% 6% 3 5% 3 2 3 2 4 5% 48%	2200
November	1st to 10th	Day	12% 5% 2 4 3 3 3 3 4 5% 57%	2058
	11th to 20th	Day	13% 8% 3 5% 3 3 3 3 4 7% 48%	1937
	21st to end	Day	16% 8% 3 5% 4 3 2 2 5% 5% 48%	1680
December	1st to 10th	Day	11% 9% 2 5% 3 2 3 2 5% 5% 53%	2690
	11th to 20th	Day	10% 9% 4 7% 4 3 3 2 3 5% 49%	3088
	21st to end	Day	19% 20% 5% 8% 4 3 4 2 4 5% 27%	4276
January	1st to 10th	Night	14% 11% 4 11% 5% 4 4 2 3 5% 37%	6018
	11th to 20th	Night	9% 7% 3 9% 6% 5% 4 3 4 5% 43%	6030
	21st to end	Night	17% 11% 4 7% 3 4 3 3 3 4 43%	6633
February	1st to 10th	Night	16% 10% 3 6% 4 3 3 3 5% 6% 41%	2601
	11th to 20th	Night	15% 10% 3 7% 4 3 3 3 4 5% 43%	2527
	21st to end	Night	14% 9% 3 6% 4 3 3 3 5% 5% 45%	1905
March	1st to 10th	Night	14% 10% 3 6% 4 3 3 3 3 5% 45%	4919
	11th to 20th	Night	11% 7% 1 4 3 3 4 3 5% 6% 53%	4980
	21st to end	Night	11% 7% 3 6% 5% 4 5% 4 6% 7% 43%	5467
April	1st to 10th	Night	11% 6% 2 5% 3 3 4 3 5% 6% 53%	2041
	11th to 20th	Night	13% 8% 2 5% 3 4 3 3 5% 7% 47%	1975
	21st to end	Night	17% 8% 3 6% 4 4 3 3 5% 7% 40%	2000
May	1st to 10th	Night	15% 8% 3 6% 3 3 4 3 5% 7% 43%	4063
	11th to 20th	Night	12% 7% 3 6% 4 3 4 4 6% 8% 43%	4053
	21st to end	Night	18% 6% 2 5% 4 3 4 3 5% 7% 42%	4260
June	1st to 10th	Night	7% 4 2 4 4 3 5% 4 7% 9% 52%	1600
	11th to 20th	Night	6% 3 1 4 4 3 4 4 8% 10% 53%	1600
	21st to end	Night	3 3 1 2 2 3 4 3 6% 10% 63%	1606
July	1st to 10th	Night	10% 5% 2 6% 4 5% 4 4 6% 9% 45%	4078
	11th to 20th	Night	4 3 2 5% 3 4 4 4 6% 9% 55%	4077
	21st to end	Night	5% 3 1 4 3 4 4 4 8% 10% 53%	4449
August	1st to 10th	Night	4 2 1 4 3 4 4 3 5% 9% 63%	2926
	11th to 20th	Night	8% 4 2 6% 4 4 5% 4 5% 8% 50%	2966
	21st to end	Night	4 3 1 4 3 3 4 3 6% 8% 62%	3586
September	1st to 10th	Night	9% 5% 2 5% 4 3 3 3 4 7% 55%	2000
	11th to 20th	Night	9% 4 2 6% 4 3 4 4 5% 7% 52%	2085
	21st to end	Night	8% 5% 2 5% 3 3 4 3 5% 6% 57%	2247
October	1st to 10th	Night	7% 4 1 4 3 3 3 3 5% 7% 62%	2400
	11th to 20th	Night	14% 5% 1 4 3 3 3 2 4 5% 57%	2400
	21st to end	Night	17% 7% 2 4 3 3 3 3 4 5% 51%	2640
November	1st to 10th	Night	12% 7% 2 3 2 3 2 2 3 5% 60%	2460
	11th to 20th	Night	12% 7% 1 4 3 3 3 3 4 6% 53%	2676
	21st to end	Night	15% 9% 2 6% 3 3 3 2 4 5% 49%	2940
December	1st to 10th	Night	10% 9% 3 6% 4 3 3 2 5% 5% 50%	4720
	11th to 20th	Night	15% 8% 3 6% 4 3 3 2 4 5% 48%	5339
	21st to end	Night	21% 17% 4 8% 4 4 3 3 4 4 29%	6938

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	48% 3 8% 24% 16% 2	4168
	11th to 20th	Day	42% 3 7% 27% 16% 5%	4170
	21st to end	Day	46% 3 8% 19% 16% 9%	4587
February	1st to 10th	Day	52% 3 9% 23% 12% 2	1800
	11th to 20th	Day	47% 3 10% 20% 16% 4	1768
	21st to end	Day	45% 3 6% 23% 16% 6%	1740
March	1st to 10th	Day	39% 3 7% 22% 18% 11%	4936
	11th to 20th	Day	32% 3 8% 24% 22% 11%	4980
	21st to end	Day	48% 5% 14% 25% 8% 1	5464
April	1st to 10th	Day	41% 3 12% 24% 18% 2	2357
	11th to 20th	Day	44% 3 13% 21% 16% 3	2374
	21st to end	Day	49% 4 11% 24% 11% 1	2400
May	1st to 10th	Day	47% 5% 12% 21% 15% 1	5872
	11th to 20th	Day	40% 6% 13% 25% 14% 2	5866
	21st to end	Day	45% 5% 12% 23% 13% 1	6626
June	1st to 10th	Day	33% 5% 17% 27% 16% 1	2800
	11th to 20th	Day	33% 5% 14% 30% 15% 2	2800
	21st to end	Day	25% 5% 17% 31% 17% 4	2788
July	1st to 10th	Day	35% 7% 14% 23% 19% 2	5836
	11th to 20th	Day	35% 7% 14% 31% 13% 1	5831
	21st to end	Day	28% 6% 20% 34% 11%	6240
August	1st to 10th	Day	26% 4 19% 29% 22% 1	4220
	11th to 20th	Day	36% 6% 15% 28% 14% 1	4126
	21st to end	Day	28% 5% 11% 36% 17% 4	4311
September	1st to 10th	Day	35% 4 12% 27% 15% 8%	2400
	11th to 20th	Day	37% 5% 9% 23% 25% 2	2310
	21st to end	Day	31% 5% 9% 26% 24% 4	2131
October	1st to 10th	Day	18% 2 6% 19% 36% 19%	3260
	11th to 20th	Day	22% 2 4 25% 34% 13%	3240
	21st to end	Day	30% 3 7% 32% 24% 4	3538
November	1st to 10th	Day	31% 3 9% 29% 23% 5%	2058
	11th to 20th	Day	37% 3 8% 23% 22% 7%	1937
	21st to end	Day	40% 3 9% 26% 21% 2	1680
December	1st to 10th	Day	36% 2 8% 36% 18% 1	2690
	11th to 20th	Day	40% 3 6% 27% 22% 2	3085
	21st to end	Day	62% 3 7% 18% 9% 1	4276
January	1st to 10th	Night	52% 3 9% 21% 13% 2	6018
	11th to 20th	Night	42% 4 7% 24% 21% 2	6030
	21st to end	Night	47% 2 7% 20% 19% 5%	6633
February	1st to 10th	Night	45% 3 11% 23% 14% 3	2601
	11th to 20th	Night	45% 3 10% 22% 17% 4	2528
	21st to end	Night	42% 2 8% 22% 19% 6%	1905
March	1st to 10th	Night	44% 2 8% 17% 23% 6%	4919
	11th to 20th	Night	33% 4 8% 23% 23% 10%	4980
	21st to end	Night	39% 6% 14% 26% 14% 1	5467
April	1st to 10th	Night	33% 4 13% 25% 21% 5%	2041
	11th to 20th	Night	37% 3 11% 24% 19% 6%	1975
	21st to end	Night	45% 3 13% 22% 16% 1	2000
May	1st to 10th	Night	41% 5% 13% 25% 13% 2	4090
	11th to 20th	Night	39% 5% 13% 24% 14% 5%	4054
	21st to end	Night	42% 7% 12% 25% 11% 3	4268
June	1st to 10th	Night	29% 6% 14% 30% 19% 3	1600
	11th to 20th	Night	24% 6% 16% 29% 21% 3	1600
	21st to end	Night	18% 5% 18% 32% 22% 5%	1606
July	1st to 10th	Night	35% 5% 13% 24% 20% 4	4035
	11th to 20th	Night	25% 5% 12% 39% 17% 1	4026
	21st to end	Night	22% 6% 18% 37% 16%	4320
August	1st to 10th	Night	20% 5% 15% 35% 23% 2	2916
	11th to 20th	Night	33% 5% 13% 30% 18% 1	2993
	21st to end	Night	21% 3 14% 37% 20% 4	3586
September	1st to 10th	Night	31% 4 11% 27% 20% 8%	2000
	11th to 20th	Night	31% 5% 10% 25% 24% 4	2085
	21st to end	Night	29% 4 7% 26% 30% 4	2247
October	1st to 10th	Night	14% 2 6% 17% 42% 18%	3920
	11th to 20th	Night	22% 2 5% 22% 30% 18%	3899
	21st to end	Night	30% 3 6% 31% 25% 5%	4252
November	1st to 10th	Night	29% 2 9% 28% 25% 7%	2460
	11th to 20th	Night	33% 2 7% 26% 25% 6%	2676
	21st to end	Night	40% 3 8% 24% 22% 3	2940
December	1st to 10th	Night	37% 3 8% 34% 17% 1	4720
	11th to 20th	Night	42% 3 7% 25% 22% 2	5341
	21st to end	Night	59% 4 9% 19% 7% 2	6938

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	22% 14% 40% 21% 4	330
	11th to 20th	Day	22% 21% 40% 16% 2	330
	21st to end	Day	18% 16% 45% 18% 3	363
February	1st to 10th	Day	26% 16% 42% 14% 2	300
	11th to 20th	Day	26% 22% 34% 15% 2	300
	21st to end	Day	27% 18% 37% 15% 2	249
March	1st to 10th	Day	22% 19% 34% 21% 4	300
	11th to 20th	Day	28% 15% 33% 20% 4	300
	21st to end	Day	28% 19% 37% 12% 3	330
April	1st to 10th	Day	23% 16% 35% 21% 5%	457
	11th to 20th	Day	20% 17% 39% 18% 6%	492
	21st to end	Day	21% 16% 30% 26% 6% 1	500
May	1st to 10th	Day	22% 10% 34% 25% 9% 1	688
	11th to 20th	Day	16% 9% 31% 26% 13% 4	725
	21st to end	Day	15% 7% 32% 25% 15% 6%	789
June	1st to 10th	Day	10% 4 19% 31% 27% 9%	730
	11th to 20th	Day	8% 3 18% 38% 27% 6%	730
	21st to end	Day	7% 3 25% 38% 22% 5%	730
July	1st to 10th	Day	11% 2 15% 30% 31% 12%	721
	11th to 20th	Day	6% 2 14% 37% 32% 9%	718
	21st to end	Day	8% 1 10% 33% 33% 14%	794
August	1st to 10th	Day	9% 2 14% 38% 31% 7%	726
	11th to 20th	Day	8% 3 13% 32% 34% 9%	670
	21st to end	Day	11% 2 11% 27% 37% 12%	583
September	1st to 10th	Day	11% 2 11% 34% 32% 11%	530
	11th to 20th	Day	9% 3 15% 37% 26% 10%	440
	21st to end	Day	12% 6% 22% 31% 20% 10%	330
October	1st to 10th	Day	9% 8% 24% 33% 20% 6%	330
	11th to 20th	Day	15% 15% 30% 27% 10% 3	330
	21st to end	Day	27% 13% 31% 23% 5%	363
November	1st to 10th	Day	14% 12% 39% 24% 9% 2	330
	11th to 20th	Day	17% 16% 36% 22% 8% 1	330
	21st to end	Day	23% 15% 34% 20% 7% 1	330
December	1st to 10th	Day	18% 14% 42% 17% 7% 2	330
	11th to 20th	Day	19% 18% 38% 18% 6% 1	330
	21st to end	Day	21% 22% 36% 18% 2	363
January	1st to 10th	Night	17% 16% 36% 25% 6%	1050
	11th to 20th	Night	18% 17% 40% 19% 4 1	1050
	21st to end	Night	18% 15% 43% 23% 2	1155
February	1st to 10th	Night	22% 13% 41% 20% 3	1001
	11th to 20th	Night	21% 15% 39% 22% 3	973
	21st to end	Night	22% 19% 36% 21% 2	585
March	1st to 10th	Night	19% 13% 38% 26% 4	600
	11th to 20th	Night	24% 13% 34% 24% 5%	600
	21st to end	Night	21% 15% 37% 23% 4	660
April	1st to 10th	Night	16% 13% 39% 27% 5%	600
	11th to 20th	Night	17% 12% 37% 28% 6%	593
	21st to end	Night	21% 11% 36% 25% 7%	600
May	1st to 10th	Night	19% 4 34% 34% 9%	600
	11th to 20th	Night	16% 4 29% 34% 17% 1	591
	21st to end	Night	13% 5% 29% 32% 19% 1	650
June	1st to 10th	Night	9% 5% 15% 43% 27% 1	600
	11th to 20th	Night	6% 2 23% 44% 25% 1	600
	21st to end	Night	3 1 21% 49% 25% 1	600
July	1st to 10th	Night	9% 2 10% 42% 32% 5%	585
	11th to 20th	Night	4 2 10% 42% 39% 3	582
	21st to end	Night	7% 2 8% 44% 35% 4	657
August	1st to 10th	Night	7% 2 8% 51% 30% 3	597
	11th to 20th	Night	7% 2 12% 49% 27% 4	594
	21st to end	Night	5% 2 10% 41% 38% 5%	660
September	1st to 10th	Night	10% 3 11% 42% 32% 3	600
	11th to 20th	Night	10% 2 12% 43% 30% 4	600
	21st to end	Night	11% 3 21% 43% 19% 3	647
October	1st to 10th	Night	8% 4 26% 38% 22% 3	800
	11th to 20th	Night	16% 7% 34% 33% 11%	800
	21st to end	Night	21% 10% 31% 29% 9% 1	880
November	1st to 10th	Night	15% 9% 37% 29% 10%	820
	11th to 20th	Night	15% 12% 37% 28% 7%	889
	21st to end	Night	22% 12% 35% 23% 8%	1050
December	1st to 10th	Night	19% 12% 38% 25% 5%	1050
	11th to 20th	Night	21% 13% 36% 26% 4	1050
	21st to end	Night	21% 14% 38% 24% 3	1155

Page generated at 2026-01-29 00:21:46. Version ac07

Copyright © 2026 Attilla Danko.